NCERT Solutions Exercise

Q1. The kidneys in human beings are a part of the system for

(a) nutrition.

(b) respiration.

(c) excretion.

(d) transportation.

Answer: (c) excretion.

Q2. The xylem in plants are responsible for

(a) transport of water.

(b) transport of food.

(c) transport of amino acids.

(d) transport of oxygen.

Answer: (a) transport of water.

Q3. The autotrophic mode of nutrition requires

(a) carbon dioxide and water.

(b) chlorophyll.

(c) sunlight.

(d) all of the above.

Answer: (d) all of the above.

Q4. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in

(a) cytoplasm.

(b) mitochondria.

(c) chloroplast.

(d) nucleus.

Answer:(b) mitochondria.

Q5. How are fats digested in our bodies? Where does this process take place?

Answer: Digestion of fat takes place in the small intestine of the alimentary canal. In the stomach, lipase acts on them and breaks down the fat. After this, the bile juice secreted by the liver in the small intestine emulsifies the fat. Pancreatic juice converts this fragmented fat into fatty acids and glycerol, thus the fat gets digested in the small intestine.

Q6. What is the role of saliva in the digestion of food?

Answer: The salivary glands present in the mouth secrete salivary juice. It contains salivary amylase enzyme. which converts starch into maltose sugar. For this reason, when you chew too many times, the food starts to taste sweet.

Q7. What are the necessary conditions for autotrophic nutrition and what are its by products?

Answer: Only green plants on earth are autotrophs which make their own food. For this some conditions are required such as:

(i) Adequate amount of water that the roots absorb.

(ii) sunlight and energy.

(iii) Carbon dioxide gas.

Q8. What are the differences between aerobic and anaerobic respiration? Name some organisms that use the anaerobic mode of respiration.

Answer: Aerobic Respiration:

(i) It occurs in the presence of air.

(ii) Glucose is completely broken down.

(iii) Its end products are: CO₂, water and energy.

(iv) Example: All higher organisms.

anaerobic respiration :

(i) It occurs in the absence of air.

(ii) Glucose is partially broken down.

(iii) Its end products: ethyl alcohol and CO₂.

(iv) Example: yeast, tapeworm.

Q9. How are the alveoli designed to maximise the exchange of gases?

Answer: The alveoli due to their balloon-like shape facilitates the exchange of air and increases the surface area. When filled with air, these alveoli expand and turn into lungs.

Q10. What would be the consequences of a deficiency of haemoglobin in our bodies?

Answer: Hemoglobin carries oxygen in our body. If their quantity decreases in red blood cells, then the organs of the body do not get oxygen smoothly. Due to which the oxidation of food is not completely done, due to which there is also a decrease in energy and tiredness arises. Due to its deficiency, a person suffers from anemia.

Q11. Describe double circulation in human beings. Why is it necessary?

Answer: Blood circulates twice in human heart. Its called double circulation. For this reason, oxygenated and deoxygenated blood remains separate from each other. If this division is not done, then both types of blood will mix and the organs will not be able to get full oxygen.

Q12. What are the differences between the transport of materials in xylem and phloem?

Answer: Carrying of substances by xylem:

(i) In this water and mineral salts flow only in the upward direction.

(ii) Convection of water and salt takes place by pressure and transpiration by traction.

  Carrying of substances by phloem:

(i) In this, the transport of food, amino acids is upward and downward in both the directions.

(ii) ATP energy is used in this.

Q13. Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.

Answer: alveoli

(i) The alveoli carries pure and impure air.

(ii) The size of the alveoli is small.

(iii) The chemical in the alveolar body is released in the form of CO₂  gas.

Renal :

(i) Nephron carries pure and impure blood air.

(ii) The nephrocytes are of large size.

(iii)Nitrogenous chemicals are released in the body in the form of urine.